The invention relates to a magnetic valve in which the electromagnet is housed outside the chamber having pressure medium passing through it, wherein a push rod connection is provided between the armature of the electromagnet and the closing body of a valve so it can be switched between a pressure source and a consumer, and more particularly wherein this push rod connection is guided through an aperture in a wall between a high-pressure chamber connectable with the source of relatively high pressure and an intermediate pressure chamber located between the high-pressure chamber and the electromagnet and which communicates with a chamber exposed to a relatively low pressure. In such a device the guide aperture is so dimensioned that on the one hand a flow of pressure medium is brought about from the high-pressure chamber to the low-pressure chamber along the push rod connection, but on the other hand the pressure drop at the aperture between the high-pressure chamber and the intermediate-pressure chamber comprises by far the greatest portion of the pressure difference between the high-pressure chamber and the low-pressure chamber and wherein the insertion of the push rod connection into the intermediate-pressure chamber from the electromagnet is sealed off by a diaphragm secured on the push rod and the valve housing.
A valve of this kind is the subject of an earlier patent application, Ser. No. 39,033 filed May 14, 1979, the entire disclosure of which is incorporated herein by reference, in the name of Heinz Leiber and assigned to the assignee of the present invention. In the subject of the earlier case, the additional characteristic is used in accordance with which a closing element to be actuated by the push rod connection interrupts, in one valve position, a flow of pressure medium from the source of relatively high pressure to the intermediate-pressure chamber.
The use of a dry magnetic circuit has the advantage that the engineer has greater freedom as to its form, method of manufacture, and the material comprising it; the magnetic circuit needs not be tightly welded or soldered. Also, in a dry magnetic circuit, valve movements are more easily ascertained by associated measuring transducers to the moving elements, which, however, can be useful in testing valve function. Furthermore, the dead time of the valve, for instance from the application of the voltage up to the movement of the armature, can be evaluated electronically and utilized for closed-loop control procedures. With this structure having separate elements, the chamber of the area through which pressure medium passes can be very much smaller; smaller pressure chambers, however, also mean that the pressure forces which must be withstood by the valve housing are smaller.
On the one hand, the usage of the invention requires a source of relatively high pressure, with the valve intended to direct the flow of pressure medium to a consumer; on the other hand, however, it also requires a low pressure chamber. Such conditions are present, for instance, in anti-locking control systems in motor vehicles, where on the one hand there is a source of brake pressure and on the other hand, the withdrawal of brake fluid, by means of valves, out of the wheel brake cylinders into a reservoir of relatively low pressure is also necessary. If, the brake pressure source is a pump having a subsequent brake control valve (full-power), then the low-pressure chamber is the brake fluid reservoir with zero pressure, while if a main brake cylinder is used as the pressure source, the withdrawn pressure fluid is withdrawn into a reservoir chamber which is at low pressure and whose contents must be reintroduced into the main pressure circuit. Other systems with similar conditions are also conceivable.
The arrangement in accordance with the invention is also applicable when gas is used as the pressure medium; however, it is primarily intended for use in hydraulic systems.